US 9,799,850 B2 · Assignee: PANASONIC CORPORATION · Inventors: Shintani; Yoichi et al.
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An organic electroluminescence (EL) device whose organic EL layer is less likely exposed to moisture. The organic EL device includes an organic EL layer; and a hygroscopic layer disposed with respect to at least one main surface of the organic EL layer. The hygroscopic layer includes: a hygroscopic film containing a base material and a hygroscopic agent mixed in the base material; and a pair of covering films each covering a different one of surfaces of the hygroscopic film in a thickness direction of the hygroscopic film. A region of the hygroscopic film that is in contact with one covering film whose distance from the organic EL layer is smaller than a distance of the other covering film from the organic EL layer contains the hygroscopic agent at a content rate lower than an average content rate of the hygroscopic agent in the hygroscopic film.
There has been used an organic EL device that for example includes, above a glass substrate, a display unit having an organic EL layer between an anode and a cathode. In recent years, there has been a demand for organic EL display devices having excellent design and mobility. An organic EL display device having excellent design for example is that with a curved display unit. An organic EL display device having excellent mobility for example is that with reduced weight. In response to the above demand, a technology has been proposed that uses, for an organic EL display device, a resin substrate (a resin film) that has flexibility and thus is bendable, instead of a glass substrate (for example, Patent Literature 1). However, a resin substrate typically does not function much as a barrier against moisture. For this reason, using a resin substrate leads to moisture intrusion into an organic
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This application is the U.S. National Phase under 35 U.S.C. §371 of International Patent Application No. PCT/JP2014/003657, filed on Jul. 10, 2014, which in turn claims the benefit of Japanese Application No. 2014-049383, filed on Mar. 12, 2014, the disclosures of which Applications are incorporated by reference herein.
The present disclosure relates to an organic electroluminescence (EL) device including an organic EL layer and a hygroscopic layer.
There has been used an organic EL device that for example includes, above a glass substrate, a display unit having an organic EL layer between an anode and a cathode.
In recent years, there has been a demand for organic EL display devices having excellent design and mobility. An organic EL display device having excellent design for example is that with a curved display unit. An organic EL display device having excellent mobility for example is that with reduced weight.
In response to the above demand, a technology has been proposed that uses, for an organic EL display device, a resin substrate (a resin film) that has flexibility and thus is bendable, instead of a glass substrate (for example, Patent Literature 1). However, a resin substrate typically does not function much as a barrier against moisture. For this reason, using a resin substrate leads to moisture intrusion into an organic EL layer through the resin substrate. This may result in a change in light-emission color, or even worse, in light emission incapability.
In view of this, a technology has been proposed that prevents moisture intrusion into the display unit (organic EL layer) by providing a hygroscopic layer between the resin substrate and the display unit to absorb/adsorb any moisture that may otherwise intrude into the display unit (for example, Patent Literatures 2 and 3).
The hygroscopic layer described in Patent Literature 2 has a configuration in which a hygroscopic film is sandwiched by a pair of inorganic films. The inorganic films are made of a material having a low moisture vapor transmission rate (indicates a degree of moisture transmission), whereby penetration of moisture into the hygroscopic layer is suppressed. Further, any moisture penetrating through the inorganic films is absorbed/adsorbed by the hygroscopic film.
The hygroscopic layer described in Patent Literature 3 has a configuration where a hygroscopic agent is mixed in an organic material, and an organic EL layer-side region of the hygroscopic layer contains the hygroscopic agent at a large amount. CITATION LIST Patent Literature
[Patent Literature 1]
Japanese Patent Application Publication No. 2009-031761
[Patent Literature 2]
Japanese Patent Application Publication No. 2012-533152
[Patent Literature 3]
Japanese Patent Application Publication No. 2001-068266 SUMMARY OF INVENTION Technical Problem
However, it has been found that organic EL layer lifespan cannot be increased by using a hygroscopic layer that includes inorganic films with a low moisture vapor transmission rate, such as those disclosed in Patent Literature 2, and that is configured so that an organic EL layer-side region thereof contains the hygroscopic agent at a large amount. That is, it has been found that such a hygroscopic layer has an insufficient moisture intrusion prevention property.
The present disclosure aims to provide an organic EL device that prevents the intrusion of moisture into an organic EL layer at a high level. Solution to Problem
One aspect of the present invention is an organic EL device including: an organic EL layer; and a hygroscopic layer disposed on at least one main surface of the organic EL layer, wherein the hygroscopic layer includes: a hygroscopic film containing a base material and a hygroscopic agent mixed in the base material; and a pair of covering films each covering a different one of surfaces of the hygroscopic film in a thickness direction of the hygroscopic film, and a region of the hygroscopic film that is in contact with one of the covering films whose distance from the organic EL layer is smaller than a distance of the other one of the covering films from the organic EL layer contains the hygroscopic agent at a content rate lower than an average content rate of the hygroscopic agent in the hygroscopic film. Advantageous Effects of Invention
In the organic EL device pertaining to one aspect of the present invention has, the region of the hygroscopic film that is in contact with the organic EL layer-side covering film contains the hygroscopic agent at a content rate lower than the average content rate. This structure, without affecting the average content rate of the hygroscopic agent in the hygroscopic layer, reduces the number of hygroscopic agent grains exposed from the hygroscopic film in the direction of the organic EL layer, and thereby reduces the number of defects in the organic EL layer-side covering film. As a result, moisture intrusion into the organic EL layer is prevented at a high level. Further, the above-described structure increases the average distance between hygroscopic agent grains and the organic EL layer. Accordingly, the probability of moisture absorbed/adsorbed by the hygroscopic agent reaching the organic EL layer can be reduced.
FIG. 1 is a cross-sectional diagram of a function device of a first embodiment.
FIG. 2 illustrates a cross-section of a hygroscopic layer.
FIG. 3 is a cross-sectional diagram of a base with the hygroscopic layer formed thereon.
FIG. 4 is a diagram for explaining the structure of a considered hygroscopic layer.
FIGS. 5A to 5D are diagrams for explaining changes in state of the considered hygroscopic layer during a manufacturing process of an organic EL device including the considered hygroscopic layer.
FIGS. 6A to 6D are diagrams for explaining changes in state of the hygroscopic layer of the first embodiment during a manufacturing process of an organic EL device including the hygroscopic layer pertaining to the first embodiment.
FIG. 7 is a schematic block diagram illustrating the overall structure of an organic EL display device pertaining to a second embodiment.
FIG. 8 is a schematic plan view diagram illustrating the arrangement of subpixels in an organic EL display panel.
FIG. 9 illustrates an A-A cross-section in FIG. 7 , viewed from the direction of arrows.
FIG. 10 is a cross-sectional diagram illustrating a part of an organic EL display panel corresponding to one subpixel.
FIG. 11 is a cross-sectional diagram of a base layer with a hygroscopic layer whose hygroscopic film includes two zero-content regions formed thereon. DESCRIPTION OF EMBODIMENTS Aspects of the Invention
One aspect of the present invention is an organic EL device including: an organic EL layer; and a hygroscopic layer disposed on at least one main surface of the organic EL layer, wherein the hygroscopic layer includes: a hygroscopic film containing a base material and a hygroscopic agent mixed in the base material; and a pair of covering films each covering a different one of surfaces of the hygroscopic film in a thickness-direction of the hygroscopic film, and a region of the hygroscopic film that is in contact with one of the covering films whose distance from the organic EL layer is smaller than a distance of the other one of the covering films from the organic EL layer contains the hygroscopic agent at a content rate lower than an average content rate of the hygroscopic agent in the hygroscopic film.
In the organic EL device pertaining to one aspect of the present invention, the above-described region of the hygroscopic film is in contact with an entirety of the above-described one of the covering films. This structure reduces the number of hygroscopic agent grains exposed from the hygroscopic film in entirety in the direction of the organic EL layer, and thereby reduces the number of defects in the entirety of the organic EL layer-side covering film. Accordingly, the probability of moisture absorbed/adsorbed by the hygroscopic agent reaching the organic EL layer can be reduced over the entirety of the organic EL layer.
In the organic EL device pertaining to one aspect of the present invention, the above-described region of the hygroscopic film has a thickness greater than an average diameter of grains of the hygroscopic agent, and the above-described region of the hygroscopic film contains the hygroscopic agent at a content rate of 5 vol % or lower. These structures ensure that an organic EL layer-side surface of the above-described one of the covering films has planarity.
In the organic EL device pertaining to one aspect of the present invention, the above-described region of the hygroscopic film contains the hygroscopic agent at a content rate of 0 vol %. This structure provides the organic EL layer-side surface of the above-described one of the covering films with a higher level of planarity.
In the organic EL device pertaining to one aspect of the present invention, the hygroscopic agent is zeolite. This structure facilitates implementation. First Embodiment
In a first embodiment, description is given on an outline of a device including a functional layer undergoing functional degradation through moisture sorption.
Description is given here on an organic EL device that includes an organic EL layer as a functional layer.
1. Overall Structure
FIG. 1 is a cross-sectional diagram of the organic EL device of the first embodiment.
The organic EL device 1 includes a display unit 7 . The display unit 7 includes an anode electrode, a cathode electrode, and an organic EL layer disposed between the anode electrode and the cathode electrode.
The organic EL device 1 includes hygroscopic layers 5 and 9 respectively disposed on the two main surfaces of the display unit 7 , and thus a hygroscopic layer is disposed on at least one main surface of the display unit 7 . In other words, the display unit 7 is sandwiched between the hygroscopic layers 5 and 9 .
Specific description is given below.
As shown in FIG. 1 , the organic EL device 1 includes a base 3 , the hygroscopic layer 5 , the display unit 7 , and the hygroscopic layer 9 disposed in the stated order. Here, the organic EL device 1 includes a surface covering layer 11 , which opposes the display unit 7 with the hygroscopic layer 9 in between. Note that the front side of the organic EL device 1 is in the direction of the surface covering layer 11 and the back side of the organic EL device 1 is in the direction of the base 3 .
Base
The base 3 has a function of supporting the display unit 7 , etc., and the hygroscopic layer 5 , the display unit 7 , the hygroscopic layer 9 , and the surface covering layer 11 are disposed (layered) on the upper surface of the base 3 .
The base 3 is made of a resin material, a ceramic material, a metal material, or the like. The organic EL device 1 pertaining to the present embodiment has flexibility and is bendable. Due to this, the base 3 is preferably formed by using a flexible resin material.
In consideration of the influence of moisture on the organic EL layer, the base 3 is preferably formed by using a material having a low transmission rate of moisture (hereinafter, referred to as a moisture vapor transmission rate). However, a resin film that is made of a resin material is preferably used as the base 3 to provide the base 3 with flexibility.
Hygroscopic Layers
Each hygroscopic layer (hygroscopic layers 5 , 9 ) has a function of preventing moisture having entered the organic EL device 1 via a surface (front or back surface) of the organic EL device 1 from intruding into the display unit 7 (referred to in the following as a moisture intrusion prevention function). The details of the hygroscopic layers 5 , 9 are described later.
Display Unit
The light emission performance of the display unit 7 is impaired by moisture having intruded into the organic EL layer, moisture absorbed/adsorbed by the organic EL layer, and the like. Specifically, the light emission performance of the display unit 7 is impaired when a change occurs in the characteristics of an organic material of the organic EL layer.
Surface Covering Layer
The surface covering layer 11 covers the display unit 7 . To be exact, the surface covering layer 11 is formed on the upper surface of the hygroscopic layer 9 in the state of a layer, and indirectly covers the display unit 7 .
The surface covering layer 11 protects the display unit 7 . Specifically, when the organic EL device 1 receives any mechanical shock, the surface covering layer 11 prevents the display unit 7 from being directly damaged. The surface covering layer 11 also has a function of preventing the penetration of moisture and/or gases such as oxygen into the display unit 7 to some extent.
The surface covering layer 11 is formed by using a material such as a resin film made of a resin material, a film of a nitride such as silicon nitride, a film of an oxide such as silicon oxide, or a metal film. The organic EL device 1 has flexibility as described above. For this reason, the surface covering layer 11 is made of a flexible resin material.
In consideration of the influence of moisture on the organic EL layer, the surface covering layer 11 is preferably formed by using a material having a low moisture vapor transmission rate. However, a resin material is preferably used for forming the surface covering layer 11 to provide the surface covering layer 11 with flexibility.
2. Hygroscopic Layer
FIG. 2 illustrates a cross-section of one hygroscopic layer. FIG. 3 is a cross-sectional diagram illustrating the base with the hygroscopic layer formed thereon.
Overall Structure
The hygroscopic layer 5 and the hygroscopic layer 9 may have the same structure or different structures. In the present embodiment, the hygroscopic layer 5 and the hygroscopic layer 9 have the same structure. As shown in FIG. 2 , each hygroscopic layer (hygroscopic layers 5 , 9 ) each include a first covering film 21 , a hygroscopic film 23 , and a second covering film 25 . In each hygroscopic layer, the first covering film 21 , the hygroscopic film 23 , and the second covering film 25 are disposed in contact with one another. This means that the front surface and the back surface (both main surfaces) of the hygroscopic film 23 are covered by the first covering film 21 and the second covering film 25 , respectively.
Each hygroscopic layer is dividable into two portions, a first portion that is close to the outside (i.e., close to the base 3 and the surface covering layer 11 ) and a second portion that is close to the display unit 7 . Each hygroscopic layer includes the first covering film 21 in the first portion and the second covering film 25 in the second portion. That is, in each hygroscopic layer, the second covering film 25 is the one of the two covering films whose distance from the display unit 7 is smaller than the distance of the other one of the two covering films from the display unit 7 .
In each hygroscopic layer, the first covering film 21 prevents moisture from the outside from intruding into the hygroscopic layer. Any moisture that passes through the first covering film 21 is absorbed/adsorbed by the hygroscopic film 23 . The second covering film 25 prevents moisture having passed through the first covering film 21 and moisture once having been absorbed/adsorbed by the hygroscopic film 23 from intruding into the display unit 7 . With this structure, each hygroscopic layer prevents moisture included in outside air from intruding into the display unit 7 . That is, each hygroscopic layer also has the function of resisting the penetration of moisture.
Covering Films
The first covering film 21 and the second covering film 25 may have the same structure or different structures. In the present embodiment, the first covering film 21 and the second covering film 25 have the same structure. For this reason, unless it is necessary to distinguish them from one another to specify arrangement position, etc., the first covering film 21 and the second covering film 25 are referred to by using the phrase “each covering film”.
Each covering film is formed by using a material having a low moisture vapor transmission rate. Specifically, a material having a lower moisture vapor transmission rate than the materials used for forming the base 3 and the surface covering layer 11 is used for forming each covering film. More specifically, each covering film has a moisture vapor transmission rate of 1×10.sup.−4 g/m.sup.2/day to 1×10.sup.−6 g/m.sup.2/day, inclusive, in an atmosphere of 40 degrees Celsius and 90% relative humidity (RH). Note that each covering film preferably has as low a moisture vapor transmission rate as possible.
One example of a material having a low moisture vapor transmission rate is an inorganic film. Examples of inorganic films include a film of a nitride such as silicon nitride, a film of an oxide such as silicon oxide, a film of an oxynitride such as silicon oxynitride, and a film of a metal oxide such as indium tin oxide (ITO) or silver oxide. Such inorganic films are formed, for example, through vacuum vapor deposition such as chemical vapor deposition (CVD) or sputtering.
Meanwhile, each covering film, when formed by using an inorganic film, has extremely small defects 31 as illustrated in FIG. 3 . The forming of such defects 31 in the manufacturing process cannot be avoided, and also, it is difficult to keep track of where the defects 31 have been formed in the manufacturing process. Accordingly, it is difficult to dispose local hygroscopic films where the defects 31 have been formed.
Here, it is assumed that moisture penetrates through the defects 31 . For example, pin holes, etc., that locally occur in an inorganic film formed through vacuum vapor deposition correspond to the defects 31 .
Hygroscopic Film
In each hygroscopic layer, the hygroscopic film 23 absorbs/adsorbs moisture having entered the hygroscopic layer. Moisture mainly enters the hygroscopic layer via the defects 31 in the first covering film 21 . Thus, the risk is reduced of moisture having entered the hygroscopic layer via the defects 31 in the first covering film 21 reaching the display unit 7 .
The hygroscopic film 23 is formed by using a material containing a hygroscopic agent 27 . Specifically, as shown in FIG. 2 and FIG. 3 , the hygroscopic film 23 contains an organic material 29 , which is one example of a base material, and the hygroscopic agent 27 mixed into the organic material 29 .
The hygroscopic agent 27 is a chemical desiccant, a physical desiccant, or the like, and is in the state of grains. Chemical desiccants take advantage of inherent characteristics (chemical reaction, deliquescence, and so on) of chemical substances, and examples thereof include calcium oxide (CaO), calcium chloride (CaCl), barium oxide (BaO), and sodium hydroxide (NaOH). Physical desiccants take advantage of the tendency of moisture molecules of adhering to porous surfaces, and examples thereof include silica gel, aluminum oxide, molecular sieve, allophane, and zeolite.
Examples of the organic material 29 include acrylic resin, polycarbonate resin, polyethylene terephthalate resin, polyvinyl chloride resin, polystyrene resin, epoxy resin, and silicone resin.
The material of the organic material 29 is appropriately selected depending on the intended use of the display unit 7 . For example, when the display unit 7 (and thus the hygroscopic layer 5 ) needs to have flexibility, a material having a low elastic modulus is preferably selected. Meanwhile, when the hygroscopic layer 5 needs to be light-transmissive, a light-transmissive material is selected. When manufacturing at a low cost is required, an all-purpose material is selected.
In the hygroscopic film 23 , the hygroscopic agent 27 is mixed with the organic material 29 such that different thickness-direction regions of the hygroscopic film 23 contain the hygroscopic agent 27 at different amounts. Specifically, a region of the hygroscopic film 23 that is in contact with the second covering film 25 , whose distance from the display unit 7 (organic EL layer) is smaller than a distance of the first covering film 21 from the display unit 7 (organic EL layer), contains the hygroscopic agent 27 at a content rate lower than an average content rate of the hygroscopic agent 27 in the hygroscopic film 23 .
The content rate (vol %) of the hygroscopic agent 27 is defined as follows. Content rate=(mass of hygroscopic agent per unit volume/mass of hygroscopic film per unit volume)×100
Alternatively, the following formula may be used to calculate content rate. Content rate=total surface area of hygroscopic agent grains observed in cross-sectional area of hygroscopic film/cross-sectional area of hygroscopic film
As illustrated in FIG. 3 , the hygroscopic film 23 includes a high-content region 23 a and a low-content region 23 b , each of which is in the form of a layer. The high-content region 23 a contains a large amount of hygroscopic agent grains 27 , whereas the low-content region 23 b does not contain much hygroscopic agent grains 27 . This low-content region 23 b is a region of the hygroscopic film 23 that contains the hygroscopic agent 27 at a content rate lower than an average content rate of the hygroscopic agent 27 in the hygroscopic film 23 .
The low-content region 23 b may not contain any hygroscopic agent grains 27 at all. Considering factors such as the planarity of the surface of the hygroscopic film 23 that comes in contact with the second covering film 25 and the occurrence of defects, the low-content region 23 b preferably contains the hygroscopic agent 27 at a content rate no greater than half of the average content rate of the hygroscopic agent 27 in the hygroscopic film 23 .
In the present embodiment, the hygroscopic film 23 includes one low-content region 23 b and one high-content region 23 a . In this situation, a virtual plane that passes through an approximate midpoint of the hygroscopic film 23 in terms of thickness and that is parallel to the main surfaces of the hygroscopic film 23 may be used as a reference. Specifically, when dividing the hygroscopic film 23 into a first portion located at a side of the virtual plane relatively close to the display unit 7 (a side closer to the second covering film 25 than the first covering film 21 ) and a second portion located at a side of the virtual plane relatively distant from the display unit 7 (a side closer to the first covering film 21 than the second covering film 25 ), the first portion (corresponding to the low-content region 23 b ) contains the hygroscopic agent 27 at a lower content rate than the second portion (corresponding to the high-content region 23 a ).
The hygroscopic film 23 can be provided with such regions containing the hygroscopic agent 27 at different content rates as explained in the following. For example, when arranging the first covering film 21 lower than the hygroscopic film 23 , the hygroscopic film 23 can be provided with such regions by taking advantage of the difference between the specific gravity of the hygroscopic agent grains 27 and the specific gravity of the organic material 29 and by curing the organic material (resin material) 29 during or after the sinking of the hygroscopic agent grains 27 . In this case, the lower portion of the hygroscopic film 23 becomes the high-content region 23 a , and the higher portion of the hygroscopic film 23 becomes the low-content region 23 b.
Meanwhile, when arranging the first covering film 21 higher than the hygroscopic film 23 , the hygroscopic film 23 can be provided with such regions by first forming a resin layer (which corresponds to the low-content region 23 b ) containing only the organic material (resin material) 29 and not containing the hygroscopic agent 27 and then forming a layer containing the organic material 29 and the hygroscopic agent 27 mixed in the organic material 29 . In this case, the earlier-formed resin layer becomes the low-content region 23 b , and the later-formed layer becomes the high-content region 23 a.
3. Manufacturing Method
The following describes one example of a manufacturing method of the organic EL device 1 .
The organic EL device 1 is manufactured through the following processes.
Preparing the base 3 (base preparation process)
Forming the hygroscopic layer 5 on the upper surface of the base 3 (lower hygroscopic layer formation process)
Forming the display unit 7 on the upper surface of the hygroscopic layer 5 (display unit formation process)
Forming the hygroscopic layer 9 on the upper surface of the display unit 7 (upper hygroscopic layer formation process)
Forming the surface covering layer 11 on the upper surface of the hygroscopic layer 9 (surface covering layer formation process)
The display unit 7 includes an organic EL layer.
The following describes these processes one-by-one.
Base Preparation Process
When using a resin material for forming the base 3 , a film of the resin material is prepared as the base 3 .
Lower Hygroscopic Layer Formation Process
The following description is provided based on an example where the first covering film 21 and the second covering film 25 are inorganic films (silicon nitride films), the hygroscopic agent 27 in the hygroscopic film 23 is aluminum oxide, and the organic material 29 is an acrylic resin material.
The lower hygroscopic layer formation process includes the following steps.
(i) Forming a silicon nitride film corresponding to the first covering film 21 on the base 3
(ii) Forming a hygroscopic film on the silicon nitride film
(iii) Forming a silicon nitride film corresponding to the second covering film 25 on the hygroscopic film
For example, in each of Steps (i) and (iii), the silicon nitride film is formed through vacuum vapor deposition (e.g., CVD).
Further, in Step (ii), the hygroscopic film is formed by applying uncured organic material (resin material) 29 containing the hygroscopic agent 27 on the silicon nitride film ( 21 ) through spin-coating for example, and then drying and curing the applied material when a predetermined amount of time has elapsed. Here, the predetermined amount of time is that required for the hygroscopic agent grains 27 to sink within the uncured organic material (resin material) 29 . This yields the hygroscopic film 23 , in which different regions in the thickness direction contain the hygroscopic agent 27 at different content rates.
Display Unit Formation Process
The display unit 7 is formed by using conventional technology.
For example, the anode is formed through vacuum vapor deposition (e.g., sputtering), the organic EL layer is formed by applying an ink containing an organic light-emitting material by using a printing method and then drying the applied ink, and the cathode is formed through vacuum vapor deposition.
Upper Hygroscopic Layer Formation Process
Similar to the above, in this process, the first covering film 21 and the second covering film 25 are inorganic films (silicon nitride films), the hygroscopic agent 27 in the hygroscopic film 23 is aluminum oxide, and the organic material 29 is an acrylic resin material.
The upper hygroscopic layer formation process includes the following steps.
(i) Forming a silicon nitride film corresponding to the second covering film 25 on the display unit 7
(ii) Forming a hygroscopic film 23 on the silicon nitride film
(iii) Forming a silicon nitride film corresponding to the first covering film 21 on the hygroscopic film 23
For example, in each of Steps (i) and (iii), the silicon nitride film is formed through vacuum vapor deposition (e.g., CVD).
Further, in Step (ii), the hygroscopic film 23 is formed as follows. First, uncured organic material (resin material) 29 not containing the hygroscopic agent 27 is applied on the silicon nitride film ( 25 ) through spin-coating for example, and then the applied material is dried and cured. Subsequently, uncured organic material (resin material) 29 containing the hygroscopic agent 27 is applied on the resin material layer not containing the hygroscopic agent 27 through spin-coating for example, and then the applied material is dried and cured. This yields the hygroscopic film 23 , in which different regions in the thickness direction contain the hygroscopic agent 27 at different content rates.
Surface Covering Layer Formation Process
In this process, the surface covering layer 11 is formed by using a resin material such as an acrylic resin. The forming of the surface covering layer 11 is performed by applying the resin material through spin-coating, and then curing the applied resin material.
4. Moisture in Manufacturing Process
Consideration
The following describes a consideration conducted by the present inventors regarding a hygroscopic layer capable of preventing moisture intrusion into an organic EL layer. Specifically, the present inventors conducted the consideration for a hygroscopic layer having a three-layer structure, namely composed of a first covering film, a hygroscopic film disposed on the upper surface of the first covering film and constituted of a resin material and a hygroscopic agent dispersed in the resin material, and a second covering film disposed on the upper surface of the hygroscopic film.
Through much consideration, the present inventors found that the organic EL layer undergoes quick degradation when a hygroscopic layer having the three-layer structure contains the hygroscopic agent at a large amount at a region thereof close to the organic EL layer.
The reasons for this are explained with reference to FIG. 4 and FIGS. 5A to 5D .
FIG. 4 is a diagram for explaining the structure of the considered hygroscopic layer. FIGS. 5A to 5D are diagrams for explaining changes in state of the considered hygroscopic layer during a manufacturing process of an organic EL device including the considered hygroscopic layer.
FIG. 4 illustrates a base 903 formed by using a resin film, and a hygroscopic layer 905 disposed on the upper surface of the base 903 . Specifically, as described above, the hygroscopic layer 905 includes a first covering film 921 , a hygroscopic film 923 , and a second covering film 925 , layered in the stated order. The first covering film 921 is formed on the upper surface of the base 903 , the hygroscopic film 923 is formed on the upper surface of the first covering film 921 , and the second covering film 925 is formed on the upper surface of the hygroscopic film 923 .
Although not illustrated in FIG. 4 , a display unit 907 including an organic EL layer is formed on the upper surface of the second covering film 925 (see FIGS. 5A to 5D ). Further, each covering film has defects 931 (e.g., pinholes) the forming of which in the manufacturing process cannot be avoided.
The hygroscopic film 923 is constituted of a hygroscopic agent 927 in the form of grains, and a resin material 929 . The hygroscopic film 923 contains the hygroscopic agent 927 in a large amount, and the hygroscopic agent grains 927 are distributed substantially evenly over the entirety of the hygroscopic film 923 . With this structure, hygroscopic agent grains 927 may be exposed at the upper surface of the hygroscopic film 923 and/or the upper surface of the hygroscopic film 923 may not have planarity (not illustrated in FIG. 4 ). Accordingly, the number of defects 931 formed in the second covering film 925 tends to increase. Note that in FIG. 4 , defects caused by hygroscopic agent grains 927 exposed at the upper surface of the hygroscopic film 923 are specifically labelled as defects 931 a.
The following explains the state of the resisting layer during the manufacturing process.
FIG. 5A illustrates a state immediately after formation of the hygroscopic layer 905 on the base 903 . The hygroscopic layer 905 on the base 903 is exposed to ambient air while being stored or when supplied to a subsequent process. While the hygroscopic layer 905 is exposed to ambient air, moisture from the air intrudes into the hygroscopic film 923 via the defects 931 (including the defects 931 a ). The moisture having intruded into the hygroscopic film 923 is then absorbed/adsorbed by the hygroscopic agent 927 , which is contained at a large amount in a region of the hygroscopic film 923 close to the second covering film 925 (close to the outside). In other words, the moisture is absorbed/adsorbed by a region of the hygroscopic film 923 close to the second covering film 925 . This state is illustrated in FIG. 5B , in which hatching is used to indicate region 939 having absorbed/adsorbed a large amount of moisture.
Subsequently, the display unit 907 is formed on the upper surface of the second covering film 925 . FIG. 5C illustrates a state immediately after the formation of the display unit 907 . Then, the hygroscopic layer 905 and the display unit 907 , as well as the base 903 on which they are disposed, are heated. This heating is performed, for example, in order to cure the resin material of the surface covering layer, and is illustrated in FIG. 5D .
During the heating, the moisture in the region 939 , which contains a large number of hygroscopic agent grains 927 having absorbed/adsorbed moisture, spreads to region 907 a , which is a region of the display unit 907 including an organic EL layer, via the defects 931 .
As such, even though the hygroscopic layer 905 exists, degradation of the organic EL device due to moisture intrusion cannot be effectively prevented.
Implementation Sample
Meanwhile, the organic EL device 1 , which includes the hygroscopic layer 5 pertaining to the first embodiment, is capable of preventing degradation due to moisture intrusion. The reasons for this are explained in the following.
FIGS. 6A to 6D are diagrams for explaining changes in state of the hygroscopic layer pertaining to the first embodiment during a manufacturing process of an organic EL device including the hygroscopic layer.
As illustrated in FIG. 3 , the hygroscopic layer 5 includes the first covering film 21 , the hygroscopic film 23 , and the second covering film 25 layered in the stated order. Although not illustrated in FIG. 3 , the display unit 7 , which includes an organic EL layer, is formed on the hygroscopic layer 5 as illustrated in FIG. 1 . Further, the first covering film 21 and the second covering film 25 have the defects 31 , the forming of which in the manufacturing process cannot be avoided as described above.
The hygroscopic film 23 contains the organic material 29 and the hygroscopic agent 27 mixed in the organic material 29 such that an upper portion thereof that includes a region that is in contact with the second covering film 25 contains the hygroscopic agent 27 at a content rate lower than the content rate of the hygroscopic agent 27 in a lower portion of the hygroscopic film 23 and an average content rate of the hygroscopic agent 27 in the hygroscopic film 23 .
With this structure, the region of the hygroscopic film 23 that is in contact with the second covering film 25 does not contain much hygroscopic agent grains 27 . Thus, not many hygroscopic agent grains 27 are exposed at the upper surface of the hygroscopic film 23 , and the planarity of the upper surface of the hygroscopic film 23 is ensured. Accordingly, the second covering film 25 does not have much defects 31 caused by hygroscopic agent grains 27 . As a matter of course, with a reduced number of defects 31 , the amount of moisture intruding into the hygroscopic film 23 can be reduced.
The following explains the state of the hygroscopic layer 5 during the manufacturing process.
FIG. 6A illustrates a state immediately after formation of the hygroscopic layer 5 on the base 3 . As described above, the hygroscopic layer 5 on the base 3 is exposed to ambient air. This leads to moisture intruding into the hygroscopic film 23 via the defects 31 . The moisture having intruded into the hygroscopic film 23 is then absorbed/adsorbed by the hygroscopic agent 927 , which is contained at a large amount in a region of the hygroscopic film 23 that is close to the first covering film 21 and distant from the display unit 7 . In other words, the moisture is absorbed/adsorbed by a region of the hygroscopic film 23 close to the first covering film 21 . This state is illustrated in FIG. 6B , in which hatching is used to indicate region 39 having absorbed/adsorbed a large amount of moisture.
Subsequently, the display unit 7 is formed on the upper surface of the second covering film 25 . FIG. 6C illustrates a state immediately after the formation of the display unit 7 . Then, heating is performed, for example, in order to cure the resin material of the surface covering layer 11 . This heating is illustrated in FIG. 6D .
During the heating, the moisture in the region 39 , which contains a large number of hygroscopic agent grains 27 having absorbed/adsorbed moisture, spreads to form a region 39 a in which moisture exists. However, due to the hygroscopic agent 27 capable of absorbing/adsorbing moisture being contained at a large amount in the region of the hygroscopic film 23 close to the first covering film 21 (i.e., a region of the hygroscopic layer distant from the second covering film 25 ) in the first place, moisture discharged from the hygroscopic agent grains 27 as a result of the heating needs to travel a long distance to reach the second covering film 25 . Accordingly, the amount of moisture penetrating through the second covering film 25 and reaching the display unit 7 is low.
As such, due to the hygroscopic film 23 in the hygroscopic layer 5 containing the hygroscopic agent 27 at a large amount in a region thereof that is distant from the display unit 7 , moisture once absorbed/adsorbed is prevented from spreading towards the display unit 7 . Accordingly, degradation of the organic EL device 1 can be prevented.
5. Hygroscopic Film
Planarity
As described above, the hygroscopic film 23 contains the hygroscopic agent 27 at a large amount at a portion thereof distant from the display unit 7 . This leads to the surface of the hygroscopic film 23 in the direction of the organic EL layer (referred to in the following as an organic EL layer-side surface) having planarity.
Specifically, it is expected that the organic EL layer-side surface of the hygroscopic film 23 would have a level of planarity not producing defects 31 when the low-content region 23 b contains the hygroscopic agent 27 at a content rate of 5 vol % or lower. Further, it is preferable that the low-content region 23 b , containing the hygroscopic agent 27 at a content rate of 5 vol % or lower, has a thickness greater than an average grain diameter of the hygroscopic agent grains 27 , and more preferably, a thickness greater than a maximum grain diameter of the hygroscopic agent grains 27 .
Here, the average grain diameter and the maximum grain diameter of the hygroscopic agent grains 27 are those determined by measuring the diameters of at least one hundred hygroscopic agent grains 27 by using a scanning electron microscope (SEM), a transmission electron microscope (TEM), or the like.
Providing the low-content region 23 b with such thickness is preferable, since with such thickness, the risk can be reduced of hygroscopic agent grains 27 being exposed from the organic EL layer-side surface of the hygroscopic film 23 even if hygroscopic agent grains 27 do exist in the low-content region 23 b.
Further, the probability of the organic EL layer-side surface of the hygroscopic film 23 having planarity is higher when the low-content region 23 b does not contain any hygroscopic agent grains 27 (i.e., the low-content region 23 b is a zero-content region), compared to when the low-content region 23 b contains hygroscopic agent grains 27 , however small in amount.
The description continues in the full USPTO document.
About 6,690 words. The USPTO PDF has it with every drawing.
Fees are due 3.5, 7.5 and 11.5 years after grant. This patent expired on October 24, 2025, so the fee marked "not paid" was the one that went unpaid.
ORGANIC EL DEVICE
Filed Jul 2014 · published Dec 2016Organic EL device
Filed Jul 2014 · granted Oct 2017Earlier publications, parents and continuations. None of them can still be enforced, or this patent would not be listed.
Prior art cited by the examiner or applicant. Useful when you check your own idea for novelty.
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